The present invention is directed, in general, to an optical fiber communications system and, more specifically, to an optoelectronic device having a P-contact and an N-contact located over a same side of a substrate, and a method of manufacture therefor.
Various optical devices, such as lasers, P-type/intrinsic/N-type (PIN) photodetectors, optical lenses, and other similar devices, are currently widely used and accepted in today""s complex optical communications systems. Currently, multiple optical devices are mounted to a substrate, such as an optical sub-assembly (OSA) or other similar substrate, for inclusion into an optical communications system. Typically, after the multiple optical devices are mounted on the substrate, contact pads and wire bonds are formed and connected, providing electrical connections to the various electrodes included within the various devices.
An example of a cross-sectional view of a conventional optical communications sub-system 100, including an optical device 105 that is mounted to an OSA 190, is illustrated in Prior Art FIG. 1, and will hereafter be described. In the current example, the optical device 105, which is illustrated as a laser or a PIN photodetector, includes an optical substrate 110 having an buffer layer 120 located thereon. The optical device 105 further includes an absorber layer 130 located on the buffer layer 120, and a cap layer 140 located on the absorber layer 130. Located within the cap layer 140 and contacting the absorber layer 130 is a P++ diffusion region 150. Likewise, contacting the P++ diffusion region 150 is a P-contact 160, and contacting the substrate 110 are N-contacts 170.
As illustrated, the P-contact 160 physically contacts a P-contact electrode 165 located on the OSA 190. However, because the N-contacts 170 are located on an opposing side of the optical device 105 from the P-contact 170, a wire bond 175 must be used to connect them to their respective N-contact electrodes 180, which are also located on the OSA 190. The inclusion of the wire bond 175 in the optical communications sub-system 100 introduces certain drawbacks, namely drawbacks associated with performance and manufacturing.
As just mentioned, the optical communications sub-system 100 experiences certain performance issues associated with the use of the wire bond 175. One of such performance issues is an undesirably high wire bond inductance. It is currently unfavorable to have such high wire bond inductance, because the high wire bond inductance causes the optical device 105 to operate slower than desired, making the device less efficient, thus less preferred in the optoelectronics industry.
As also just mentioned, the optical communications sub-system 100 experiences certain manufacturing limitations associated with the use of the wire bond 175. Because the wire bond 175 must be attached to both the N-contacts 170 and N-contact electrodes 180, an additional complex manufacturing variable has been added to the process flow. Such additional complex manufacturing variables are generally unwanted, especially when they may cause up to a 2 percent reduction in optical communications sub-system 100 yields. While the reduction in optical communications sub-system 100 yields may be attributed to many things, it may particularly be attributed to the inherent difficulty in creating a wire bond to a silicon or an indium phosphide substrate, such as used in the N-contacts 170 or the OSA 190.
Some of the difficulties associated with wire bonding in optical devices are demonstrated with respect to Prior Art FIG. 2. More specifically, Prior Art FIG. 2 illustrates micrographs 210, 220, 230 depicting examples of damage that may be caused while bonding a wire bond 240 to an optical device 250. In a typical situation, such a damaged optical device 250 would subsequently be discarded, substantially increasing manufacturing costs. Likewise, because the wire bond 240 is also coupled to another device, such as an OSA, damage caused while bonding the wire bond 240 to the optical device 250 may also cause a fully assembled OSA, including multiple lasers, PIN photodetectors and lens, to be damages and also subsequently discarded. Additionally, not only does the inclusion of the wire bond 240 cause yield problems, it also adds additional manufacturing time, which one skilled in the art knows is undesirable.
Accordingly, what is needed in the art is an optical device and a method of manufacture therefor, that overcomes the deficiencies in the prior art, such as the problems associated with the use of wire bonds in optical devices.
To address the above-discussed deficiencies of the prior art, the present invention provides an optoelectronic device and a method of manufacture therefor. The optoelectronic device includes an optical active layer formed over a substrate and an active region formed in the optical active layer. The optoelectronic device further includes a P-contact and an N-contact formed over a same side of the substrate and associated with the active region.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.